K here's one gripe with the Presto card. So shuffling along between people tapping, you tap your card but weren't sure if it tapped or not. Loud busy vehicle, crowded, did I hear my one beep or not, or wasn't watching the screen closely. So tap again to be sure, says "declined". Shouldn't it say "fare paid", or flash green. Why red and declined if it's been paid and has been accepted. Can understand pass-backs, so just have a yellow screen or something that says 'fare already paid'.
Also they gotta fix the colour of cards for child Presto. It's hitting the fan and more are catching on. What better way to evade fares than to use an identical looking card everyone else is using, tap like everyone else, and legitimately "pay" your fare with the bells and whistles telling everyone that it's been paid. Gotta have a different colour card.